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    <!-- 打印出1000-2000年中所有的闰年，并以每行四个数的形式输出 -->
    <script>
        var a=0;
        for(var year=1000;year<=2000;year++){
            if((year%4==0 && year%100>0)||year%400==0){ 
                console.log(year)
            }
        }       
    </script>
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